Exhaust emission control

ABSTRACT

A method of operating an internal combustion engine (20) in order to improve the control of the level of emissions in the exhaust gases, comprising the steps of, at least when the engine (20) is operating under idle and/or low load conditions at a temperature below a predetermined value, applying a parasitic load to the engine (20) to increase engine fuel demand, and increasing fueling rate to the engine (20) in response to said engine fuel demand to thereby raise the temperature of the exhaust gases. The method may further comprise the steps of raising the temperature of the air being inducted into the engine (20) and/or directly heating a catalyst (25) in the engine exhaust system (24), conveniently by respective heater elements (23,26) coupled to an alternator (27) driven by the engine (20).

This invention relates to the controlling of the operation of internalcombustion engines, in order to improve the control of the level ofemissions in the exhaust gases, particularly during engine warm-ups.

It is recognised that it is generally more difficult to control thelevel of exhaust emissions and to achieve stable operation of an enginein the low load range, as compared with the higher ranges of engineload. It is also recognised that these difficulties increase when theengine is at a low operating temperature, such as may exist after aninitial start up of the engine.

Further, in regard to engines operating with catalytic converters in theexhaust system, these catalysts do not become effective until they havereached an effective operating temperature generally referred to as"light off" temperature of the catalyst. This light off of the catalystis generally dependent upon the heat input to the catalyst by theexhaust gases and this is dependent upon the exhaust gases being of asufficiently high temperature to rapidly effect heating of the catalystto light off temperature.

It is therefore the object of the present invention to provide a methodand means for operating an internal combustion engine which willcontribute to overcoming or reducing the above problems and to theachievement of improved control of the exhaust emissions.

With this object in view, there is provided according to the presentinvention, a method of operating an internal combustion engine,characterised by, at least when the engine is operating under idleand/or low load conditions at a temperature below a predetermined value,applying a parasitic load to the engine to increase engine fuel demand,and increasing fueling rate to the engine in response to said enginefuel demand to thereby raise the temperature of the exhaust gases.

By raising the temperature of the exhaust gases, the rate of rise of theoperating temperature of the engine and of the temperature of thecatalyst is increased, thus the engine reaches stable operatingconditions more quickly and the period of time required to light off thecatalyst is reduced, thus reducing the period of engine operationwithout effective treatment of the exhaust gases by the catalyst.

It will be appreciated that the use of the parasitic load is not alwaysnecessary at all engine start ups; as where the engine has previouslybeen operating, the operating temperature of the engine and thetemperature of the exhaust gases may be sufficiently high to achievequickly effective operation of the engine and light off of the catalyst.Accordingly, in order to obtain improved fuel efficiency, the parasiticload is only applied to the engine when start up occurs while thetemperature of the engine is below a predetermined value, that valuebeing selected for the particular engine to be a temperature at whichthe engine will operate at an acceptable level of stability and lightoff of the catalyst will be achieved within a relatively shortacceptable time interval from engine start up.

It has been found that the present invention is particularly relevant tothe operation of two stroke cycle engines as such engines have lessbuilt in running loads and generally lower exhaust temperatures thanfour stroke cycle engines that incorporate valve mechanisms which applya significant load to the engine. However, it is to be understood thatthe present invention does have application to engines operating on thefour stroke cycle and will, in such engines, contribute to improvementin the stability of the engine operation and the effectiveness of thecatalyst system.

The method of the present invention may be further characterised byraising the temperature of the air being inducted into the engine ordirectly heating the catalyst in the exhaust system. It is to beappreciated that the raising of the temperature of the inducted air willfurther contribute to increasing the rate of rise of the operatingtemperature of the engine, and raising the temperature of the exhaustgases, each of which will contribute to reducing the period required toobtain the effective operation of the exhaust system catalyst. Further,the direct heating of the exhaust system catalyst will also contributeto increasing the rate of rise of the temperature of the catalyst and toreducing the period required to light off the exhaust catalyst.

Although the load applied to the engine in accordance with the presentinvention is referred to as a parasitic load, it is to be understoodthat it is possible to make use of the energy resulting from theapplication of such load to the engine, however that energy isnevertheless energy which would not normally be required or producedduring operation of the engine.

A convenient parasitic load can be achieved by coupling an electric loadto the alternator normally provided in an engine installation to providethe electrical energy for operation of the engine. Thus the parasiticload may take the form of switching on some or all of the lights in thecase of a motor vehicle, or may be in the form of providing heat energy,such as for heating the incoming air to the engine, or for heating thecab or passenger area of a vehicle.

Further, the load on the engine can be increased by restricting thecirculation of the cooling water or air to thereby increase the loadapplied to the engine by the water or air circulation pump or compressoror fan. If the engine is selectively couplable to a compressor such asan air compressor or air conditioning compressor, that compressor may beused to apply the parasitic load to the engine.

The application of a parasitic load in the form of an electric heaterelement coupled to the engine driven alternator would result in thegeneration of heat energy. Such heat energy can be usefully applied inheating the air being inducted into the engine thereby raising thetemperature of the inducted air, or directly heating the catalyst in theexhaust system. Such useful applications of heat energy will effectivelycontribute to reducing the period required to light off the exhaustcatalyst.

There is thus also provided a management system for an internalcombustion engine, characterised in that said system comprises an ECUarranged to receive input signals relating to engine operatingconditions to determine the required fueling rate to the engine, engineloading means, and fuel supply means; said ECU being programmed to, atleast when the engine is operating under idle and/or low load conditionsat a temperature below a predetermined value, control said loading meansto apply a parasitic load to the engine to increase engine fuel demandand said fuel supply means to increase fueling rate to the engine inresponse to said engine fuel demand to thereby raise the rate ofincrease of the temperature of the engine exhaust gases.

The system of the present invention may comprise fluid circulating meansdriven by the engine to circulate engine cooling fluid and circulationcontrol means to selectively restrict the circulation of the enginecooling fluid for applying said parasitic load. Alternatively, anelectric load means may be coupled to an alternator driven by the enginefor applying said parasitic load. The electric load means may preferablyinclude a heater element.

Conveniently, the controlling of the application of the parasitic loadand the period of its application is under the control of the ECU whichis normally incorporated as part of the management system of mostinternal combustion engines where fuel efficiency and exhaust emissionsare important factors.

In the accompanying drawings:

FIG. 1 illustrates diagrammatically a convenient arrangement of the ECUand other componentry suitable for carrying out the present invention;and

FIG. 2 illustrates an internal combustion engine provided with practicalmeans for carrying out the present invention.

Referring to FIG. 1, the ECU 10 has input signals relating to enginetemperature, engine load and engine speed. The power supply to the ECU10 is from the battery 11 or alternator 12, depending upon the conditionof the battery, and output of the alternator as determined by thecut-out 13. The battery 11 is provided as the power supply storage andis charged by the alternator 12, which is driven by the engine.

The relay 15 controls the power supply to the heater element 16 and therelay 15 is controlled by the ECU 10 through the switch 17. The ECU 10is programmed to determine during the start up procedure whether theengine temperature is below a predetermined value below which it isdesirable to provide assistance to obtain an acceptable level ofstability of engine operation and rapid light off of the catalyst. Atypical predetermined value of temperature is 35° C.

As previously indicated, under some start up conditions, the engine mayalready be at an effective operating temperature as a result of theengine having not cooled down from a previous period of operation, andin such circumstances the use of a parasitic load to reduce the warm uptime is not required. Also if the power supply from the battery 11 isbelow a preset value, such as 10 volts in a normal 12 volt battery, theECU 10 will not proceed with the application of an electric, parasiticload since this would be an unacceptable load on the battery 11 and maybe detrimental to the operation of the ECU 10.

Where the ECU 10 determines from the battery condition and the enginetemperature that a parasitic load should be applied, the ECU 10activates the relay 15 which will couple the heater element 16 to thealternator 12. The resulting increase in engine load will increase thefuel demand of the engine and the ECU 10 will appropriately increase thefuel supply to the engine. The combustion of the resulting increasedamount of the fuel will result in an increase in the temperature of theexhaust gases, which in turn will result in an increased rate of rise ofthe temperature of the engine and the exhaust catalyst, with a resultingreduction of the time taken to reach stable operation of the engine andto light off the catalyst.

The ECU 10 can be programmed to switch off the parasitic load inaccordance with the achieving of a preset condition, which may be theengine reaching a preselected temperature, or may be purely on a timebasis, either a real time from start up or a time corresponding to theengine having completed a preselected number of revolutions since startup.

It has been found convenient and desirable to locate the heater element16 in the path of the air being inducted into the engine so as toincrease the temperature of that air as delivered to the combustionchamber, thereby resulting in an increase in the temperature of thesubsequently generated exhaust gases.

It has also been found that the heater element 16 can be located in theexhaust system to directly heat the catalyst therein, thereby inducing aquick light off of the catalyst and obtaining effective operation of theexhaust system.

The use of a heater element as a parasitic load has been found to be oneof the most convenient forms of load to apply to the engine as theenergy from the heater element can also be used advantageously inachieving the more rapid warm up of the engine and raising thetemperature of the exhaust gases and inducing rapid light off of theexhaust catalyst.

Referring to FIG. 2, the engine 20 is provided with fuel supply meanscomprising injector means 21 and has air induction system 22 and exhaustsystem 24. Air can be inducted into the engine 20 through the airinduction system 22 and generated exhaust gases can be treated in theexhaust system 24 for controlling the level of exhaust emissions.Catalyst 25 are provided in the exhaust system 24 for that purpose.

The engine 20 drives alternator 27 and compressor or pump 28 via a belt29. The alternator 27 provides the electric power for operation of theengine 20 and the pump 28 provides for the circulation of engine coolingfluid. It is appreciated that an increased load on the alternator 27 orthe compressor or pump 28 would also result in an increased load on theengine 20.

Electric heater element 23 is located inside the induction system 22 andcan be connected as part of an electric load to the alternator 27 forapplying a parasitic load to the engine 20. The heater element 23 can beused to apply heat to the inducted air and thus raise the temperature ofthe inducted air.

Another electric heater element 26 is located inside the exhaust system24 and can also be connected as part of the electric load to thealternator 27 for applying a parasitic load to the engine 20. The heaterelement 26 can be used to directly heat the catalyst 25 in the exhaustsystem 24 and induce quick light off of the catalyst for the effectiveoperation of the exhaust system.

The pump 28 may be fitted with circulation control means in the form ofa variable opening valve or adjustable vent for selectively restrictingthe circulation of the engine cooling fluid. Such restriction wouldresult in an increased load on the pump 28 and therefore an increasedload to the engine 20.

The claims defining the invention are as follows:

I claim:
 1. A method of operating an internal combustion engine,characterised by, at least when the engine is operating under idleand/or low load conditions, determining when the engine temperature isbelow a predetermined value, automatically applying a parasitic load tothe engine in response to determining said engine temperature is belowsaid predetermined value to thereby increase the engine fuel demand, andincreasing fuelling rate to the engine in response to said increasedengine fuel demand to thereby raise the temperature of the exhaust gas.2. A method according to claim 1, characterised in that the parasiticload is applied by restricting the circulation of engine cooling fluidby fluid circulating means driven by the engine.
 3. A method accordingto claim 1, characterised in that the parasitic load is applied bycoupling an electric load to an alternator driven by the engine.
 4. Amethod according to claim 3, characterised in that said electric loadincludes a heater element.
 5. A method according to claim 4,characterised by applying the heat generated by said heater element toraise the temperature of the air being inducted into the engine.
 6. Amethod according to claim 4, characterised by applying the heatgenerated by said heater element to directly heat a catalyst in theengine exhaust system.
 7. A method according to claim 1, furthercharacterised by raising the temperature of the air being inducted intothe engine.
 8. A method according to claim 1, further characterised bydirectly heating a catalyst in the engine exhaust system.
 9. Amanagement system for an internal combustion engine, characterised inthat said system comprises an ECU arranged to receive input signalsrelating to engine operating conditions to determine the requiredfuelling rate to the engine, engine loading means, and fuel supplymeans; said ECU being programmed to, at least when the engine isoperating under idle and/or low load conditions, determine when theengine temperature is below a predetermined value, control said loadingmeans to apply a parasitic load to the engine in response to determiningsaid engine temperature is below said predetermined value to therebyincrease the engine fuel demand and adjust said fuel supply means toincrease fuelling rate to the engine in response to said engine fueldemand to thereby raise the temperature of the engine exhaust gases. 10.A system according to claim 9, characterised in that said loading meansinclude fluid circulating means driven by the engine to circulate enginecooling fluid and circulation control means to selectively restrict thecirculation of the engine cooling fluid for applying said parasiticload.
 11. A system according to claim 9, characterised in that saidloading means include an electric load means coupleable to an alternatordriven by the engine for applying said parasitic load.
 12. A systemaccording to claim 11, characterised in that said electric load meansincludes a heater element.
 13. A system according to claim 12,characterised in that said heater element is arranged to raise thetemperature of the air being inducted into the engine.
 14. A systemaccording to claim 12, characterised in that said heater element isarranged to directly heat a catalyst in the engine exhaust system.
 15. Asystem according to claim 11, characterised in that the ECU is poweredfrom an electric energy storage coupled to an alternator driven by theengine, said ECU is programmed to only apply said electric load when thelevel of said storage is above a preset value.
 16. A system according toclaim 9, characterised in that the ECU is programmed to control theperiod of the application of the parasitic load.
 17. A system accordingto claim 16, characterised in that the period is determined by theoperating temperature of the engine.
 18. A system according to claim 16,characterised in that the period is determined by the number ofrevolutions from the engine start up.
 19. A system according to claim16, characterised in that the period is determined by a preselected timeinterval from the engine start up.
 20. A system according to claim 9,characterised in that the input signals relate to the enginetemperature, engine load and engine speed.
 21. A system according toclaim 9, characterised in that a heater element is provided to raise thetemperature of the air being inducted into the engine.
 22. A systemaccording to claim 9, characterised in that a heater element is providedto directly heat a catalyst in the engine exhaust system.